Researchers at the U.S. Geological Survey National Wildlife Health Center in Madison, Wis., use eggs to see if the Asian strain of the H5N1 bird flu virus has entered the U.S. in this photo from 2006. Andy Manis/AP hide caption

itoggle caption Andy Manis/AP

Mosquitoes like this one can carry the virus that causes dengue fever, which may become a bigger problem in some regions as biodiversity is lost. James Gathany/CDC Public Health Image Library hide caption

itoggle caption James Gathany/CDC Public Health Image Library

Kathy Del Tonto (far right) participates in a class that teaches school cafeteria workers how to prepare meals from scratch. LiveWell Colorado hide caption

itoggle caption LiveWell Colorado

Photographer Freya Najade journeys into the weird sci-fi world of Europe's agricultural production. In one cow-milking facility she visited, "two people are needed to milk twice a day 300 cows," she writes. Freya Najade hide caption

itoggle caption Freya Najade

John Kelly and Dr. Marcia Angell were advocates on opposing sides of a Massachusetts measure to legalize physician-assisted suicide. Jesse Costa/Jesse Costa/WBUR hide caption

itoggle caption Jesse Costa/Jesse Costa/WBUR

Dr. Jame Abraham used positron emission tomography, or PET, scans to understand differences in brain metabolism before and after chemotherapy. Dr. Jame Abraham hide caption

itoggle caption Dr. Jame Abraham

Visitors to one Kansas City hospital will no longer be able to buy a Big Mac on the premises. Keith Srakocic/AP hide caption

itoggle caption Keith Srakocic/AP